1. Field of the Invention
The disclosure relates to an optical system.
2. Description of Related Art
The solar simulator is a major apparatus for inspecting the photoelectric conversion efficiency of the solar cell and the photovoltaic module, which is quite important for the research and the verification of the products in the solar energy industry. The known solar simulator can be divided mainly into a flash type and a continuous exposure type according to the technique of the light source. The flash type solar simulator has the advantage of low cost and simple design. The continuous exposure type solar simulator can provide the exposure similar to the real solar light, so that the measurement error caused by the transient effects can be avoided when the continuous exposure type solar simulator is applied. Furthermore, the continuous exposure type solar simulator can be combined with other testing methods such as heating exposure, measurement exposure, etc. for performing the test in the same apparatus. Hence, the continuous exposure type solar simulator has favorable utility.
The solar simulator is required to have certain performance in at least the three aspects including the spectral match, the non-uniformity of irradiance on the test plane, and the temporal instability of irradiance. The improvement of the non-uniformity of irradiance on the test plane mostly emphasizes on the light distribution design of the light source, the adjusting of the relative position of the light source, and the dispositions of the reflective or scattering elements, which is still difficult for the continuous exposure type solar simulator having a light sources array with large area to achieve the requirement of good uniformity of irradiance on the test plane which can be smaller than 2%.
The continuous exposure type solar simulator with large exposure area generally requires the use of an array of a plurality of lights to obtain the test condition of 1000 W/m2 radiation. However, owing that the ray radiation from the plurality of lights can be overlapped and interfered mutually and the scattering light is difficult to be eliminated, the distribution of the ray radiation is complicate and difficult to properly controlled or adjusted by the prior art. In addition, as described in above, the method for controlling the non-uniformity of irradiance on the test plane of the continuous exposure type solar simulator with large exposure area mostly emphasizes on the light distribution design of the light source, the adjusting of the relative position of the light source, the dispositions of the reflective or scattering elements, etc. Such methods of locally adjusting the relative positions of the components may have influence on the light intensity of other regions where the relative positions of the components are not changed, so that the ray radiation distribution of the exposure area must be modulated again, which is time-consuming, difficult to maintain, and failing to efficiently reduce the non-uniformity of irradiance on the test plane. By using the solar simulator to perform the test on the photovoltaic module, the measurement error is not easily to be reduced.